Centrisweep



Oct. 14, 1958 F. COOK ETAL 2 CENTRISWEEP Filed Sept. 6, 1956 r 3Sheets-Sheet 1 if f/ m 14/ 1 I Z4 1/ 1/ I Q55 .17 l:

Oct. 14, 1958 H. F. COOK ,ET AL 2,856,124

CENTRISWEEP Filed Sept. 6, 1956 V 3 Sheets-Sheet 2 Oct. 14, 1958 H. F.COOK ET AL 2,856,124

CENTRISWEEP Filed Sept. 6, 1956 I5 Sheets-Sheet 3 United CENTRISWEEPApplication September 6, 1956, Serial No. 608,337 6 Claims. (Cl. 233-7)This invention relates to a centrifugal separator of the type having asweeper blade for sweeping the interior of the centrifuge bowl to removethe solid particles of the centrifuged material from the bowl endwisethereof, the separation of the solid particles from the liquid beingcarried out by centrifugal sedimentation.

One object of the present invention is to provide a centrifugalseparator of the foregoing type constructed and arranged to handle aslurry containing friable solid par ticles with a minimum of degradationand attrition of the particles.

Another object is to provide a separator of the type described capableof handling liquid suspensions of fibrous material without jamming andwith a minimum of tearing or degradation of the fibers.

Another object is to provide a centrifugal separator of the typedescribed having an improved construction in which the interior rotatingassembly as a whole can be dynamically balanced.

Another object is to provide a centrifugal separator for which means fordriving the sweeper blade are shielded from contact with the material tobe centrifuged.

Still another object is to provide such a separator in which therelative movement of the centrifuge bowl and of the sweeper blade issuch that each particle of centrifuged material swept out of the bowlfollows a smoothly curved path of the same geometrical shape across theinterior of the bowl, the periphery of the sweeper blade beingmaintained perpendicular to the path of sweeping at each point on thepath to minimize the shearing, or fracturing forces on any solidparticles being swept out.

A further object is to provide such a separator in which the rotationalspeed of the sweeper blade about its own axis is substantially constant,thereby maintaining a substantially uniform load on the sweeper bladerotating mechanism and avoiding problems of backlash.

Other and further objects will be apparent from the drawing and from thedescription which follows:

In the drawings:

Fig. l is a view in side elevation, partly broken away and in section,of one embodiment of the invention;

Fig. 2 is a view in end elevation of the embodiment shown in Fig. 1;

Fig. 3 is a view in section taken along the line 3-3 of Fig. 1;

Fig. 4 is a view in elevation of the sweeper blade;

Fig. 5 is a view in side elevation on an enlarged scale, partly brokenaway and in section, showing the manner in which the sweeper blade ismounted within the rotary bowl;

Fig. 6 is a view in cross-section showing another embodiment of theinvention; and

Fig. 7 is a view in cross-section showing still a third embodiment ofthe invention.

Referring to Fig. 1, the device of the present invention comprises ahousing 10 mounted on a support 12 having an outlet 14 for liquidefliuent material. A pair of pedestates atent ice A tals 16, 18 supportmain bearings 20, 22 in which are journaled aligned hollow shafts 24,24'. Sheave 26 is secured to the flanged end of shaft 24 by means ofbolts 28, 28 and is driven from motor 30 by means of belt 32.

Rotary bowl 35 is supported between and secured to opposing ends ofshafts 24, 24 by means of spiders 36, 36, bowl 35 being located withinstationary housing 10 and being ro'tatabiy driven together with shafts24, 24' by means of motor 3% (Fig. 2).

At the opposite end of shaft 24 and driven therefrom is a differentialdrive mechanism 34 of the type described in Piper U. S. Patent 1,962,461granted June 12, 1934. Within the interior of hollow shaft 24 is mounteda second shaft 33 supported by bushing 39 and driven from drivemechanism 34, which may be adjusted to provide any desired speed ratiobetween shafts 24 and 38. It will be understood that any other suitablemeans may be provided for maintaining a predetermined differentialbetween the speeds of the two shafts. in practice it has been found thata ratio of the order of 144:143 is satisfactory but it will beunderstood that the ratio may be varied over a wide range.

Shaft 38 serves to support and rotate a hub member 46 (Fig. 5) bolted toa flanged end 48 of shaft 38 within rotary bowl 35 so that bowl 35 andhub 46 have a common axis of rotation. Hub 46 is provided withdiametrically opposing passages 50, 5t) connecting the :interior of hub46 with the interior of rotary bowl 35, and is supported at its oppositeend by bushing 39 on hollow shaft 38, being secured thereto by boltingto flanged end 48'. The free end of shaft 38 is positioned by thrustbearings 51 within sheave 26.

Extending through hollow shaft 38 is a stationary influent supply pipe52 mounted on bracket 54 which is secured to pedestal 18. An aperture 56adjacent the inner closed end 58 of supply pipe 552 at the center of hub46 is provided to introduce the liquid influent or slurry into theinterior of the device, the infiuent passing through apertures 56, St inhub 46 as the latter rotates.

A pair of oppositely disposed efiiuent discharge pipes 69, 60 extendinwardly from the periphery of rotary bowl 35, each pipe beingadjustable in position and provided with a deflector 62 which serves todeflect influent slurry as it emerges through openings and prevent lossof feed solids into the filtrate.

Sweeper blade 64 (Fig. 4-) has a generally closed periphery matchingthat of theinterior of bowl 35, being preferably of generally circularconfiguration and is mounted on hub 2-6 (Fig. 5) for rotation about itsown axis of symmetry, as represented by a line passing through thecenter of blade 64 perpendicular to the plane defined by its periphery.The axis of symmetry of blade 64 intersects the aXis of rotation of bowl35 and of hub 46 at an acute angle, so that as bowl 35 rotates withrespect to hub 46 about their common axis of the plane of rotation ofthe blade oscillates with respect to the bowl with the margin orperiphery of the blade sweeping across substantially the entire innerface of the shell from end to end. At every position of blade 64,opposite portions of its periphery extend adjacent opposite ends of bowl35. To permit simultaneous rotation of blade 66 about its own axis ofsymmetry, it is secured to bearing ring 70 and to ring gear 72 by meansof bolts 74, 74. Ring gear 72 is provided with a radially outwardlyextending flange 76 which is engaged by an overlying shoulder of lockingring 78 which in turn is secured to a flan R6 of hub 46 by means ofbolts 80. 80. Two O-rings 32-, 82 are provided to seal ring gear 72 fromcontact with the slurry entering the hub a d rotarv she l thronsh inlet56.

Meshing with ring gear 72 and serving to drive the same is a pinion gear84 mounted for rotation about shaft-38.and keyed at 86 to shaft 24 forrotation therei ring 885 i's k secured in place-on shaft 38 .by-means*of-" a snapring. Seals9 0,,*9tl arejprovided' to prevent access. of theslurry or its components to" the shaft bearings-or to the' gears, whileseal9li-serves tocontain the lubricantfor the gears. Boltedto'hub 46-and extending. axially outwardlylbeyond rotary bowl 35 are members92;92'

which. serve to balance the unsymmetrical distribution of mass ofrhub46, ring gear 72 and blade 64, and also serve as plows to remove fromthe. interior of spokes 96. of. spider 36'. any accumulated materialwhich tends to. build; up. in. these locations.

Because of the 2:1 ratio between ring gear 72. and pinionv 84. andthespeed differential between bowl 35 and" hub46 .(on which sweeper plate64 is mounted), bowl 35. advances 90 with-respect tosweeper blade 64during each.one-halfrev-olution of thesweeper blade about the axis ofbowl 35. Accordingly, it is necessary to provide four gaps or apertures65, 65 (Fig. 4) which are 90. apart in the. periphery of sweeper blade64 to permit itto. pass the two discharge pipes 60, 60 during its.sweeps. Since the path across the face of bowl 35 traced by theseapertures is dilferent during the return half of the sweep of blade 64,any particulate materiallleft during the first half of the sweep in thetrack of the gaps 65 is swept out during the return half. Blade 64lmayalso be provided with ribs 66, 66 which serve both as reinforcing orstrengthening elements and as deflectors tending to prevent materialfromsliding across the face of rotating blade 64 and through gaps 65, 65

Bafiles 100,100, 102, 102 are provided within the interior of stationaryhousing 16 to compartmentalize this housing and separate the centralzone between baffle members 102, 102 into which discharge pipes 60empty, from the side compartments adjacent spiders 36,316, Accessopenings provided with removable covers, 104, 104may be provided at anysuitable locations about stationary housing It). A labyrinth type sealbe tween shaft 24 and housing It) is provided by means of fiinger plates106, 166 which are secured to shaft 24 adjacent the end walls of housingIt). Semi-circular shields 108, 1% are provided extending inwardly fromthe walls of housing 10 and overlying the upper half of fiinger plates106, 106 as seen in Fig. 5 to deflect toward the interior of housing anymaterial running down the walls of the housing.

In operation of the device, rotary bowl 35 is driven together with shaft24, 24 at any suitable speed, say from 1000 to 3000 R. P. M., in thecase of a machine having a bowl 35 which is inches in diameter, by meansof motor 30, belt 32 neously hub 46 is driven from shaft 38 throughdrive mechanism 34 at a slightly lower speed, hub 46 rotating in thesame direction as rotary bowl 35. When bowl 35,, for example, is drivenat 1800 R. P. M. and the speed ratio in drive mechanism 34 is 144:143,the speed of hub 46 is l787 /2 R; P.'M., so that bowl rotates at a speedof 12 /2 R. P. M. with respect to hub 46., This difference in speed maybe varied without limit, but preferably is from 4 to 40 R. P. M. Becauseof this speed diiferential the plane defined by the outer periphery ofsweeper blade 64 mounted on hub 46' oscillates with respect to bowl 35,sweeping from one end oftthe bowl adjacent shaft 2.4.',.the number ofcycles per minute being equal to the speed differential, which in thespecific example given above is. at the ratio of 12 /2 cycles perminute. Furthermore, sweeper blade 64 is simultaneously rotated aboutits own axisof symmetry bythe interaction of ring gear 72and pinion 84,so that the total speed'of rotation of the sweeper blade about the axisof the hub and sheave 26. Simultashaft 24 to the other end adjacent gwhich 'itis introduced thereafter.

is dififerent from the speed of the bowl and the speed of the hubandmidway between these two speeds--when the ratio of ring gear 72 topinion 84 is 2:1. That is, the speed of blade 64 about its own axis ofsymmetry is 6% R. P. M. with respect to the hub 46. According ly, theapparent speed of blade 64 with respect to bowl 35 (measured abouttheaxisof rotation of bowl 35) is also 6% R. P. M., the speed of blade64 about the axis of the hub being interm'ediatethe speed of the hub andof sweeper blade 64; simultathev bowl. This rotation neously about two"diver gent axes causes each portion of the periphery of blade64 tosweep across the inner face of bowl 35 with the blade being maintainedsubstantially-perpendicular to the directionof sweep at each point alongthe path and with a minimum of shearing effect upon the material beingswept out of bowl 35, as will be explained more fully hereinafter.

The slurry which is to be separated into its solid andliquid componentsis introduced through inlet pipe sea-11 emerges through aperture intothe interior of rotary bowl by centrifugal force as bowl '35 rotates.Because the slurry is" equally divided between of which is always onthe'opposite 35. ,-Inother words, theinfluent slurry is depositeduniformly andprogressively on 35, in synchronismwith thesweepingadvanceof: sweeper pipes 60; 60 whence it baffiestfiz, 162; ber 112st thewithdrawn through: effluent pipe passes into thezone between While. thesclidparticulate material-Ht) is accumulating in a layer adjacent theinner'face of rotary bowl35i sweeper blade 64Zis sweeping slowly backand forth and sweeps the solid material toward spiders'36, 36 until abed of solid material has accumulated in the form shown in Fig-5.

from. the surface of the faces 114, ments of housing 10.Itfwill'be'noted that of outlet pipes 60, 66 is adjusted liquid withinrotary shell 35 reaches to a point-between pipes 68 and the outermargins of faces 114. That portion of the arcuate faces 114 togetherwith any portion of the bed of solid particles beyond'the margin oftheliqu'id may be termed a beach are swept orscraped by blade '64."This'mode of operation permits substantially complete separation of.I'the' solid and liquid phases as the -solid is swept across the beach.by sweeper blade 64; Any solid material'iinpinging upon the inner faceof'spokes plows 92, 92 and'the solid material the position drops out thebottom of the side compartments of housing 10, into any suitable" 56into the interior of hub 46 whence it passes through passages50, 50 35,on opposite sides" of sweeper blade 64, andimpinges upon the inner faceof the generally cylindrical bowl35; being held in'place passages 50, 50each side of'sweeper'blade 64 fromthe other aperture, there-is abalancedload on' opposite faces of the sweeper blade as well as onbowl-- the inner face of have" as shown 'in' 110 'hav'e been" separatedbegins to-overflowthe innerl'nargin of outlet of'housing It) andaccumulates in chambottom of housing 10 whence it maybe 14 at the samerate at Thereafter each sweep of sweeper blade'64 scrapes-all additionalcentrifugally settled solid material bed and sweeps it'across arcuate11-4 of spiders '36, 36 into the side compartso that thelevel of acrosswhich the sblidparticles 96, 96 is: removedbr the bed of solid material110 and the beach. This con- -struction and mode of operation providesfor a direct push upon each solid particle substantially in thedirection of travel of the particle at all times and moves each particleout of rotary bowl 35 with a minimum shearing effect of sweeper blade 64upon solid particles.

This minimal shear effect provides improved operation of the device whenseparating frangible or friable crystalline materials from liquidslurries. The solid material separated from the slurry by the action ofthe present device is remarkably free from broken or fracturedparticles, as well as free from scratches on the smooth faces of theparticles, a feature which is particularly important in the case ofcertain crystalline materials such as sugar and a variety of otherorganic and inorganic crystalline solids. The minimal shear effect alsomakes the machine of the present invention particularly useful forseparating fibrous material from liquid suspensions with strikinglyimproved results as compared with conventional centrifugal separators.When used with such fibrous suspensions the machine is remarkably freefrom jamming, does not appreciably tear or degrade the fibers, andprovides highly effective separation of liquid from the fibers.

As pointed out above, the solid portion of the slurry may be allowed toaccumulate within rotary bowl 35 to form a bed across the surface ofwhich fresh solid material is swept out of bowl 35 by means of sweeperblade 64. However, in the embodiment shown in Fig. 6, the accumulationof the bulk of this solid material is rendered unnecessary by theprovision of filler members 120, 125) made of any suitable material suchas rubber, plastic, stainless steel, etc., and shaped to provide agenerally spherical inner surface for bowl 35. This embodiment providesfor use of the machine with slurries containing solids which mightdecompose if allowed to stand for appreciable periods of time.

There is shown in Fig. 7 still another embodiment of the invention inwhich sweeper blade 130 is rigidly secured directly to hub 132 as bybolting thereto. In this embodiment of the invention, in which sweeperblade 130 rotates about only a single axis of rotation, namely the axisof rotation of hub 132 and of rotary bowl 35, there is a small amount ofshear between the face of the sweeper blade and the particles of solidmaterial being swept out of bowl 35. However, only two apertures 65, 65in the periphery of sweeper blade 130 which are 180 apart are requiredin this embodiment, in order to clear any given number of outlet pipesprovided they all lie in the same plane perpendicular to the axis ofrotation. In addition, in this embodiment the bowl 35 may be polygonalinstead of circular in cross-sectional configuration and blade 130 mayhave a mating or matching polygonal periphery. Indeed, in thisembodiment blade 130 may be polygonal even when bowl 35 is cylindricalor spherical, the centrifugally settled solid particles building up onthe inside of bowl 35 providing a configuration which matches that ofblade 130. While this small amount of shear may be tolerated in the caseof certain solid materials without producing excessive fracturing ortearing of the solid material, the embodiments of Figs. 5 and 6 in whichthe sweeper blade 64 rotates about its axis of symmetry are preferred.

Although specific embodiments of this invention have been describedherein, it is not intended to limit the invention solely thereto but toinclude all of the obvious variations and modifications within thespirit and scope of the appended claims.

We claim:

1. A centrifugal separator comprising a rotary bowl, a hub mountedwithin said bowl for rotation about the axis of rotation of said bowl, asweeping blade mounted on said hub within said bowl, said blade having apcriphery lying generally in a plane, the axis of symmetry normal tosaid plane intersecting the axis of rotation of the bowl at an acuteangle with opposite portions of the periphery extending adjacentopposite ends of the bowl, said blade being mounted for rotation withrespect to the hub about said axis of symmetry, and means for rotatingsaid bowl and said hub simultaneously at different speeds in the samedirection about said axis of rotation and for simultaneously rotatingsaid blade about said axis of symmetry at a speed different from boththe speed of the bowl and the speed of the hub about said axis ofrotation while maintaining a fixed ratio between the speed of the bowland that of the blade to cause the blade to sweep the bowl from end toend and to remove material from the bowl endwise thereof.

2. A centrifugal separator as defined in claim 1 in which the hub andbowl both rotate in the same direction with the hub rotating at a speedless than that of the bowl, and the apparent rotation of the blade aboutthe axis of rotation of the bowl is in the same direction as the hub andbowl and at a speed intermediate that of the hub and that of the bowl.

3. A centrifugal separator as defined in claim 1 in which the differencein speed between the hub and the bowl is from 4 to 40 revolutions perminute, and the speed of the blade is approximately onehalf of saiddifference.

4. A centrifugal separator comprising a rotary bowl, a hub mountedwithin said bowl for rotation about the axis of rotation of the bowl, asweeping blade having a closed periphery lying generally in a planemounted on said hub within said bowl with the axis of symmetry normal tothe plane of the periphery of the blade intersecting the axis ofrotation of said bowl at an acute angle whereby opposite portions ofsaid periphery extend adjacent opposite ends of said bowl, means forrotating said bowl and said hub simultaneously in the same directionwhile maintaining a fixed ratio between the speed of the bowl and thatof the hub, and drive means interconnecting said bowl and said blade forsimultaneously rotating said blade about said axis of symmetry at aspeed different from both the speed of the hub and the speed of the bowlwhile maintaining a fixed ratio between the speed of the bowl and thatof the blade, whereby the periphery of the blade sweeps the interior ofthe bowl from end to end to remove therefrom endwise of the bowl aportion of the centrifuged material.

5. A centrifugal separator as defined in claim 4 in which the drivemeans includes a gear mounted for rotation with said bowl and a secondgear intermeshing with the first mounted for rotation with said bladeabout said axis of symmetry and in which said hub includes means forshielding said gear from contact with the material being centrifugedwithin said bowl.

6. A centrifugal separator comprising a rotary bowl, a hub mountedwithin said bowl for rotation about the axis of rotation of the bowl,means for rotating said bowl and hub simultaneously while maintaining afixed ratio between the speeds thereof with the speed of the bowlexceeding that of the hub by 4 to 40 revolutions per minute, a sweepingblade having a generally circular periphery mounted on said hub forrotation about the axis of symmetry of the periphery of the blade, saidaxis of symmetry intersecting the axis of rotation of the hub and bowlat an acute angle whereby opposite portions of the periphery extendadjacent opposite ends of the bowl, the blade sweeping the interior ofthe bowl from end to end upon rotation of said bowl and hub to removeendwise of the bowl a portion of the centrifuged material, and meansinterconnecting said bowl and blade for simultaneously rotating theblade about said axis of symmetry while maintaining the speed of theblade with respect to the hub about said axis of symmetry equal to afixed fraction of the difference in speed between the hub and the bowl.

References Cited in the file of this patent UNITED STATES PATENTS2,414,421 Small Ian. 14, 1947 UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION Patent No, 2,856,,124 October 14, 1958 Horace F. Cook et alwIt is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction and that the saidLetters Patent should read as corrected belowa Column 6, line 49, for"gear" read m gears 0 I (SEAL) Attest:

KARL HQ AXLINE ROBERT C. WATSON Attesting Oflicer Commissioner ofPatents

